/*
 * Type-safe wrapper for WebGL in GWT.
 * 
 * Copyright (C) 2009 Hao Nguyen
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package gwt.g3d.resources.client.impl;

import gwt.g3d.resources.client.ExternalImageResource;
import gwt.g3d.resources.client.ExternalTexture2DResource;
import gwt.g3d.resources.client.ImageElementResource;
import gwt.g3d.resources.client.Texture2DResource;

import com.google.gwt.resources.client.ResourceCallback;
import com.google.gwt.resources.client.ResourceException;

/**
 * Abstract implementation of {@link Texture2DResource}
 * 
 * @author hao1300@gmail.com
 */
public abstract class AbstractExternalTexture2DResource 
    implements ExternalTexture2DResource {
  
  /**
   * Helper method for loading a texture.
   * 
   * @param externalImageResource
   * @param textureResource
   */
  protected void getTexture(ExternalImageResource externalImageResource,
      final ResourceCallback<Texture2DResource> callback) {
    externalImageResource.getImage(new ResourceCallback<ImageElementResource>() {
      @Override
      public void onSuccess(ImageElementResource resource) {
        onImageLoaded(resource, callback);
      }
      
      @Override
      public void onError(ResourceException e) {
        callback.onError(new ResourceException(e.getResource(), 
            e.getMessage()));
      }
    });
  }
  
  /**
   * Overrides this method to handle the event when the requested image
   * is successfully loaded.
   * 
   * @param imageResource
   * @param textureResource
   */
  protected abstract void onImageLoaded(ImageElementResource imageResource,
      ResourceCallback<Texture2DResource> textureResource);
}
